Abstract

For the first time brachiopods are described from the Late Silurian Shishtykskaya Suite of the West Sajan comprising 36 species
belonging to 31 genera and 21 families. The new species Altajella sajanica, Stegerhynchus dicbotomus and the new genera and species
Sajanospirifer uriensis and Meristoidea asiatica are established. In the upper part of the Shishtykskaya Suite there is a Pridolian complex of
species and also a Ludlovian unit. Biostratigraphic correlation of the Upper Silurian of West Sajan with similar age strata from Tuva, Gorny
Altai, and Salair is provided. The Subrianid Fauna (Concbidium, Lamelliconcbidium) belongs to part of the Uralian-Cordilleran Region,
occupying the northeastern territory of the West Sajan sea, while the Tuvaella Fauna (Central Asian Province) occupied the southwestern
part of this sea. Both biogeographical units are subdivisions of the Uralian-Cordilleran Region. The Central Asian Province includes benthic
assemblage 2 (including the Tuvaella Community), and the Subrianid Fauna, Uralian-Cordilleran Region benthic assemblage 3 brachiopods
(including the Pentamerus and Concbidium communities). The most important factor in their distribution was probably water depth and
also salinity related to the large land (Angarida) on the north. The boundary between the biogeographic units is an area in the West-Sajanian
sea.